Declarative Access to Filesystem Data : New application domains for XML database management systems

XML and state-of-the-art XML database management systems (XML-DBMSs) can play a leading role in far more application domains as it is currently the case.Even in their basic configuration, they entail all components necessary to act as central systems for complex search and retrieval tasks. They provide language-specific indexing of full-text documents and can store structured, semi-structured and binary data.Besides, they offer a great variety of standardized languages (XQuery, XSLT, XQuery Full Text, etc.) to develop applications inside a pure XML technology stack. Benefits are obvious: Data, logic, and presentation tiers can operate on a single data model, and no conversions have to be applied when switching in between.This thesis deals with the design and development of XML/XQuery driven information architectures that process formerly heterogeneous data sources in a standardized and uniform manner. Filesystems and their vast amounts of different file types are a prime example for such a heterogeneous dataspace. A new XML dialect, the Filesystem Markup Language (FSML), is introduced to construct a database view of the filesystem and its contents. FSML provides a uniform view on the filesystem’s contents and allows developers to leverage the complete XML technology stack on filesystem data.BaseX, a high performance, native XML-DBMS developed at the University of Konstanz, is pushed to new application domains. We interface the database system with the operating system kernel and implement a database/filesystem hybrid (BaseX-FS), which is working on FSML database instances. A joint storage for both the filesystem and the database is established, which allows both developers and users to access data via the conventional and proven filesystem interface and, in addition, through a novel declarative, database-supported interface. As a direct consequence, XML languages such as XQuery can be used by applications and developers to analyze and process filesystem data. Smarter ways for accessing personal information stored in filesystems are achieved by retrieval strategies with no, partial, or full knowledge about the structure, format, and content of the data (“Query the filesystem like a database”).In combination with BaseX-Web, a database extension that facilitates the development of desktop-like web applications, we present a system architecture that makes it easier for application developers to build content-oriented (data-centric) retrieval and search applications dealing with files and their contents. The proposed architecture is ready to drive (expert) information systems that work with distinct data sources, using an XQuery-driven development approach. As a concluding proof of concept, a complete development cycle for an OPAC (Online Public Access Catalogue) system is presented in detail